Calutron ion source slit cleaner



Aug. 25, 1959 A. M. STARR 2,901,619

CALUTRON ION SOURCE SLIT CLEANER Filed Oct. 8, 1946 4 Sheets-Sheet 1/Nve/vrof? ALLA/v M 5 714m? A TroR/vax n A. M. STARR 2,901,619

CALUTRON ION SOURCE SLIT CLEANER Aug. 25, 1959 Filed oct. 8, 1946 4sheets-sheet 2 lill-I \65 m Elk-7 E da /NVENTOR ALLA/v M. STARR @yATTORNEK Aug- 25, 1959 A. M. STARR CALUTRON ION SOURCE SLIT CLEANER 4Sheets-Sheet 3 Kw Filed Oct. 8, 1946 Aug. 25, 1959 A, M STARR 2,901,619

' cALuTRoN 10N SOURCE SLIT CLEANERl Filed Oct. 8. 194e 4 sheets-Sheet 4INVEN TOR. ALLA/v M 5MP/ l@ BY A rro/e/VEK 4United States PatentCALUTRON ION SOURCE SLIT CLEANER Allan M. Starr, Piedmont, Calif.,assignor to the United States of America as represented by the UnitedStates Atomic Energy Commission Application October 8, 1946, Serial No.701,905

4 Claims. (Cl. Z50-41.9)

The present invention relates to calutrons and more particularly to animproved arc slit cleaning device used in association with a calutronion source.

A calutron is a term which has been defined as any apparatus or machinewherein isotope separation or enrichment is achieved on a large scale,using commercially useful quantities of one or more isotopes byappropriate separative action on gaseous ions with electrostatic orelectromagnetic means or combinations of them. The foregoing definitionhas been taken from the application for LettersI Patent of the UnitedStates, Serial No. 5 57,784, byErnest O. Lawrence, now Patent No.2,709,222, issued May 24, 1956. In that patent, the theory of ionicseparation and the principles of operation of a calutron are so fullytreated and thoroughly explored that no useful purpose would be servedby here repeating the discussion contained therein. Y

In general, however, an ion source of a calutron projects ions into amagnetic field; thereafter, the ions travel in curved paths through themagnetic field, the ions of greater mass describing paths with curves oflonger radii than the ions of'lesser mass. Isotope collectors aredisposed at suitable points along each path, preferably at the 180 pointwith respect to the source of the beam, and collect the isotopes of thedifferent masses. In this manner, the atoms of different mass that wereoriginally in a polyisotopic mixture are substantially separatedfromeach other, one mass being enhanced with respect to one isotopewhile the other is correspondingly impoverished with respect thereto.

Successful operation o-f a calutron depends upon the fulillment of manyunique conditions. For example, the ion source, the region surroundingthe beam, andthe isotope collectors must be enclosed within a reducedpressure vessel evacuated to the order of -5 to 104' mm. Hg. Suchmatters are hereinafter referred' to but briefly, as it is with the ionbeam producing mechanism, or source unit of the calutron with which thepresent invention is concerned.

A source unit for a calutron generally includes a chamber for holding aquantity of material, such as uranium tetrachloride, capable of beingvaporized, a heater for the chamber, a cathode and an anode forestablishing an arc discharge, and accelerating electrodes; thearrangement of these components being such that when heat is applied tothe chamber by suitable means, the material vaporizes and is thencedrawn through the electron stream of the arc discharge wheredissociation takes place. The ions are thence drawn through a slit bythe accelerating electrodes to form a beam which in turn is projectedinto the magnetic field as heretofore described. Therefore it isemphasized, that in the operation of a calutron, it is necessary tovaporize the material desired to be ionized. Consequently there iscreated a problem related to the condensation of such vapor on theVvarious operative parts of the device and the subsequent encrusting ofthe various operative parts with condensed vapor.

A More particularly there is created the specific problemA ICC ofcondensation of vapor on the sides of the arc' slits whereby theformation of an excessive amount. ofthe condensed vapor, or crud, willseriously interferewith the calutron operation; Crud is described as a.hard deposit of decomposed charge material, usually collecting on theare slits or adjacent. thereto,` and is largely metallic.

In order to continue operation of they calutron itis necessary to removethis crud at regular periods during such operation and to this end thepresent invention com'- prises a calutron source embodying an improved?device for removing encrusted materials adhering to the arc slits of acalutron ion source.

Heretofore, contributions to the art of slit cleaning as applied tocalutron ion source units havecomprised various means and have been usedwith varying success,

' none of them, however, being capable of decrudding'the arc slitswithout subsequent damage to the slits or to the adjacent parts orotherwise failing because of their own mechanical structurel andcomposition to perform the function for which they were designed. Morespecifically, considerable failure and consequent discontin-nance ofoperation of the calutron has been associated' with slit cleaneroperation due to the binding of the cleaner blocks along the length ofthe arc slits and also failure and termination of operation due tobinding of the mechanical linkage systems employed to project the slitclean-` er blocks along the length of the arc slits. p

It is therefore an object of this inventionl to produce an ion beam moreefficiently, to decrease operational shutdown of the calutron and toprevent damage to arc chamber slits by providing an improved slitcleaning device to remove encrusted materials from the beam definingelements of a calutron ion source.

It isV another object of this invention to provide a calutron ion sourceslit cleaner comprising a means for projecting the cleaning blocks in astraight line along the are slits of a calutron ion source withoutbinding within the arc slits and without damage to the said slits.v Y

Another object is to provide av linkage and operating mechanism forprojecting the slit ycleaner blocks in a straight line along the lengthof the slits without binding of the component parts of the said linkageand operating mechanism.

Still another object is to provide a slit cleaner comprising a means foroperating the saidV slit cleaner from' Fig. 2 is an enlarged sectionaldetail of a source unit as shown in Fig. 1, embodying the presentinvention and being `taken on line 2 2 of Fig. 5; Y

Fig. 3 is a sectional view onl a plane indicated by theY line 3 3 ofFig. 2;

Fig. 4 is an enlarged View on a plane indicated by the' line 4 4 of Fig.2;

Fig. 5 is an enlarged view taken on line 5--5 of Fig."

. l showing the faces of the ion source chambers; and:

Fig. 6 is an isometric view of one of the scraper slides shown indetachedposition.

Referring to the drawings and more particularly'to graphite Fig. 1,there is illustrated a calutron including an electro#- magnet 13 havinga pair of opposing pole pieces, .onlyone of which, number 14, is shown,between whichisY positioned a vessel 16 adapted to be evacuated bysuit.- able pumps (not shown). The vessel 16 includes atop. wallv 17,. abottom wall 18, a rear Wall 19, side walls 20-21 and a removable frontwall or door 22. Mount-4 ed on the removable door 22 and projecting intothe evacuated vessel 16 is an ion generating and transmitting mechanismindicated generally by 10, a beam liner 11, and isotope collectorsgenerally indicated by 12.

Referring to Figs. 2, 3, 4 and 5, the ion generating and transmittingmechanism Ml comprises suitable charge reservoirs 23-24 within which arepositioned removable charge bottles 26-27 adapted to be illed with acharge material such as uranium tetrachloride. This uraniumtetrachloride charge material will vaporize when heated, such heatusually being supplied by electrical heaters as indicated by the numeral25 on the drawing. The charge reservoirs 23-24 are provided with vapormanifolds 28-29 communicating with ionizing chambers 31--32 in which aredisposed suitable baflles 3.3-34 adapted to break up the vapor flow andthus provide a uniform distribution of the vapor within the ionizingchambers 31-32. It is well understood in calutron operation that thevapor of the charge material will ow under pressure from the chargebottles into the vapor manifolds and thence through the baffles into theionizing chambers.

The ionizing chambers 31-32 have the form of elongated slots and eachchamber is provided with a cover plate 36-37 incorporating a V-shapedbeam defining slit 38-39 generally of the length of the ionizingchambers 31-32, and disposed centrally thereof.

The source l@ also includes a pair of cathode stems 1 and 2 shown inFig. l and Fig. 5 having their end portions overlying one of theextremities of the chambers 31-32, and in which are positioned suitableelectron emissive cathodes 3 and 4, best shown in Fig. 5 electricallyconnected to leads entering through the cathode stems so that when acircuit is closed an electron stream is caused to ow the length of theionizing chambers 31-32 to movable anodes 94-86 positioned at the otherextremity of the chambers 31-32 and connected by any suitable leads, inthe manne-r known in the art, to an electrical circuit (not shown). Thiselectron stream ionizcs the charge vapor, the vapor being thenceprojected into the magnetic field by means of accelerating electrodesand 6 shown in Fig. 1, which accelerating electrodes are likewiseconnected to any suitable circuit, not shown. Forming a part of themajor supporting structure of the source there is a rectangular framecasting 41 having a plurality of perpendicular legs attached thereto.Two of these perpendicular legs, 42, 43 are spaced apart on oppositeends of the casting 41 and together they support the brass frame casting44 extending from one leg 42 to a point overlying the other leg 43. Theguide frame casting 44 incorporates a machined guide slot 46 generallyof its entire length, and into which is inserted the hatchet 47 which issecurely attached by welds to the projecting lever arm 48.

The guide frame casting 44 also supports the triangular bell crank plate49, one fulcrurn point 49a of which is rotatably attached thereto bymeans of the pivot pin 51 threaded into the guide frame casting 44 andsecured in place by the castellated nut 52. Another fulcrum point 4911of the bell crank 49 is rotatably attached to the link arm 48 by meansof the pin 53 and is secured in position by the castellated nut 54, andstill another fulcrum point 49C of the bell crank 49 is rotatably aixedto the offset link 56 by means of the pin 57 which is secured in placeby a cotter pin.

The end of the lever arm 48 opposed to the hatchet 47 is rotatablyattached to the linkage arm 58, the linkage arm 5S being slotted toreceive the lever arm 48 and both arms 4S and 58 are joined by means ofthe pin 59 loosely fitted within an aligned machined hole in the arms 48and 58 and is retained in place by means of a Cotter pin. The other endof the linkage arm 58 is rotatably positioned on the frame 41 and issecured thereto by the threaded shoulder pin 61 which is loosely fittedin the linkage arm 58 but securely clamped to the frame 41 by means ofthe castellated nut 62.

The other end of the offset link 56 opopsed to the fulcrum point 49C isrotatably attached to the push-pull rod 63, the push-pull rod 63 beingprovided with a slot to receive the offset link 56 and both of thesemembers are joined by the pin 64 which is retained in place by means ofa cotter pin.

The fulcrurn pins 5l, 53, 57, 59, 6l, and 64 are preferably fabricatedof a durable metal such as Ampco, a copper base alloy that combinesgreat strength and wear resisting qualities and are therefore utilizedas an effective means to prevent binding of the pins employed in thelinkage system.

The lever arrn 43 projects beyond the hatchet 47 and is there providedwith a cylindrical boss 66 rigidly fixed at right angles thereto andextending for equal lengths on each side thereof. The boss 66 isaccurately drilled and reamed of its entire length to tightly receivethe rod 67 and the rod 67 is further secured to the boss 66 by a cotterpin to prevent rotation of the rod 67 within the boss 66. The ends ofthe rod 67 project beyond the ends of the boss 66 and are freely engagedwithin the slotted holes 68--69 of the cross piece lugs 71--'72; theslotted holes 68-69 being of such length as to provide a freelongitudinal motion of the rod 67 therein. The lugs 7 1-72 are firmlyattached by welding to the slide cross piece 73; the cross piece 73being of a length corresponding to the spaced-apart distance of theionizing chambers .3l-32. Each end of the slide cross-piece 73 is bent96 to provide entrance into the arc slit openings 38-39 where theyengage the scraper slides 7 4-7 6 and are secured thereto by tightlyfitted pins 77-78.

The scraper slides 74-76 support thin scraper blades 79-81 positioned atan angle on the scraper slides 74--76 and within the arc slits 253-39.The blades 79--81 are V shaped and correspond closely to thecrosssectional area of the arc slits 33-39 and have 30 bevelled edges onthe three sides thereof to provide a cutting edge that engages theparallel sides of the arc slits 358-39. The blades 7981 being preferablyformed of a hard and tough material, such as stainless steel, aresuitable for use in scraping and removing the decomposed charge materialor crud adhering to the arc slits 38-39- Attached to the scraper slidepieces 74-76 by means of the shoulder screws 82-83, but situatedinteriorly of the arc members Slt-4&2, are graphite scraper slides84--86 that are generally of the width of the arc chambers 31-32. Thescraper slides 34-86 are utilized to scrape condensed materials from thesides and front walls of the arc chambers 31-32 and, during operation ofthe calutron, are also used as anodes for the electron stream emittedfrom the cathodes. During operation of the calutron, the scraper slides84-86 functioning as anodes are positioned at the end of the arcchambers 31-32 opposing the cathodes.

Thus it is shown that the linkage system of the slit cleaner is looselycoupled to the slit cleaning system of the device so that when thepush-pull rod 63 is projected in the direction indicated by the arrow87, motion in the direction indicated by the arrow S8 is transmitted tothe hatchet 47 by means of the bell crank 49 and attached links 48-56,causing the hatchet 47 to slide along the slotted guide 46 and also atthe same time projecting the scraper slides 74-76-79-81-84- and 86 bymeans of the cross piece 73, along the length of the arc slits 38-39.

The hatchet 47 and accompanying scraper slides 74 76-79-81-84- and 86are also returned to the op-l erating position by means of applying amotion to the push-pull rod 63 in the direction indicated by the arrow89. The length of the sliding motion of the hatchet 47,`

within the groove 46 is limited by the threaded regulating stop-screws91--93 which are positioned on the end of the guide casting 44 and arelocked by means of the hexagonal nuts 92-94.

The threaded stop-screws 91-93 have slots 95 milled in one end thereofby means of which they are rotated to provide adjustment of the lengthof travel, of the hatchet 47; adjustment being necessary to limit travelof the slit cleaning scraper slides 74-76 along the length of the arcslits 38--39.

Although it is not shown on the drawings, it is generally understoodthat the push-pull rod 63 is operable from outside the evacuated vessel16 and enters it by means of a vacuum seal housing mounted on theexternal side of the door 22 and having means such as a conventionalseal on the interior thereof permitting of the longitudinal movement ofthe rod 63 without breaking the vacuum seal.

While there is herein disclosed what is at present considered apreferred embodiment of the invention, it will be understood thatvarious changes and modifications may be made therein, and it isintended to cover al1 such changes and modifications as come Within thetrue spirit and scope of the appended claims.

What is claimed is:

1. Apparatus for projecting an ion beam comprising vwalls defining anevacuated vessel, ion generating chambers having beam defining slitstherein, Scrapers mounted in the slits for longitudinal movementtherein, means comprising a bell crank, scraper-actuating linkagemembers associated with said bell crank, a hatchet associated with saidlinkage members, a guide casting having an elongated slot adapted toreceive the said hatchet therein, stops positioned at opposite ends ofthe said guide casting for limiting longitudinal movement of the saidhatchet along the said slot and means connecting said linkage and saidscrapers for compelling longitudinal movement of the said Scrapers alongthe said beam dening slits.

2. In combination with an ion generating chamber having an elongatedexit slit therein, means for removing deposits from said slit andincluding, a scraper mounted in said slit for longitudinal reciprocatingmovement therealong, an actuating rod attached to said scraper, a bellcrank pivoted upon a stationary support, means for rotating said bellcrank, and a rotary to translatory movement converting linkage joiningthe bell crank and actuating rod, thereby to reciprocate said rod in afixed plane upon rotation of the bell crank and to move the scraperalong the slit without binding.

3. Apparatus as dened in claim 2 wherein said scraper comprises a irstportion adapted to scrape the edge of the slit nearer the generatingchamber and a second por- 'tion adapted to scrape the edge of the slitfarther from the generating chamber.

4. Apparatus as defined in claim 2 wherein said chamber and said scraperactuating assembly are mounted upon a framework disposed interiorly ofan evacuated Vessel.

No references cited.

